1. Field of the Invention
The present invention relates to an apparatus for sending and to an apparatus for receiving a digital broadcast signal having multiplexed program information and video content coded for image compression.
2. Description of Related Art
FIG. 15 is a block diagram of a prior art transmission apparatus 502 and receiving apparatus 503. As shown in FIG. 15 the transmission apparatus 502 has an MPEG-2 Video-compliant (ISO/IEC 13818-2) video encoder 56, an MPEG-2 Audio-compliant (ISO/IEC 13818-3) audio encoder 57, program-specific information generator 59, and an MPEG-2 Systems-compliant (ISO/IEC 13818-1) multiplexer 66.
The receiving apparatus 503 has a demultiplexer 107, video decoder 112, and audio decoder 113.
Also shown in the figure are the digital video input signal 49, digital audio input signal 50, audio bitstream 64, video bitstream 76, program-specific information 500, multiplexed bitstream 501, video bitstream 110, audio bitstream 126, digital video signal 111, and digital audio signal 114.
The video encoder 56 of this prior art transmission apparatus 502 compresses the digital video input signal 49 according to the MPEG-2 Video standard to output video bitstream 76. The digital audio input signal 50 is similarly compression-coded by the audio encoder 57 to output MPEG-2-compliant audio bitstream 64. The program-specific information generator 59 generates program-specific information (“PSI” below) 500 describing the relationship between the video bitstream 76, audio bitstream 64, and program number. The multiplexer 66 then multiplexes the video bitstream 76, audio bitstream 64, and PSI 500 and outputs multiplexed bitstream 501.
The demultiplexer 107 of this prior art receiving apparatus 503 then demultiplexes the received multiplexed bitstream 501 into the video bitstream 110 and audio bitstream 126. The video bitstream 110 is then decompressed by the video decoder 112 and output as digital video signal 111. The audio bitstream 126 is likewise decompressed by the audio decoder 113 and output as digital audio signal 114.
Problem to be Solved by the Invention
A problem with the prior art system described above is that the audio and video bitstreams are not encrypted, and can be easily stolen by an unauthorized receiving apparatus.
Another problem is that even if the bitstreams are encrypted there is no protection against the encryption method itself being broken. More specifically, there is no means for preventing unauthorized reception of data sent by the transmission apparatus.
The present invention is directed to solving these problems, and an object of this invention is to provide protection assuring that data sent by the transmission apparatus can be safely received by the receiving apparatus.